I think this piece suffers from you using your photo reference too directly. It literally looks like you just
took a bunch of photo and sandwiched them together with very little effort to integrate them. You
would be much better off starting with a single line drawing, or rough block in of the scene using no
photography, and only then using photo reference more like texturing.
The lighting throughout does not match. Since the whole scene is being lit by the sun, there should be
only one lighting direction. Yet the trees are light from the front, the arch from the front, and the
surrounding buildings have a strong rim light. Then we see the sun spitting out god rays, so we know
the actual location of the light, but nothing in the scene is effected by it.
Also, watch the scale of buildings. That tower on the right hand side is all out of scale with the
buildings behind it. I guess you could argue it is much further in the forground, but it doesn't look
that way. It looks like the railings around it are 25 feet high in comparison to the building complex
I suggest going back to the drawing board, sketch out an idea, and work over that. Don't go right to
photo reference--you will just end up with a montage like you have here.
Hope that helps a bit!
"Art is not a matter of what you can see, but what you can make other people see."